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AS Physics new spec HELP!

Please help with this question! here is the question and the mark scheme:

physics3.png

Mark scheme:
Attachment not found




The part I don't understand is: path difference = 2 * distance moved
(edited 7 years ago)
Physics32.png30.3KB
Reply 1
Avatar for Someboady
Someboady
OP
17
Bump!
Reply 2
Avatar for sue99
sue99
10
Original post by Someboady
Please help with this question! here is the question and the mark scheme:

physics3.png

Mark scheme:
Attachment not found




The part I don't understand is: path difference = 2 * distance moved


Can you please include a picture of Figure 1? as I believe this question is connected with harmonic/fundamental frequencies and I need to see the diagram to be sure
Reply 3
Avatar for Someboady
Someboady
OP
17
Original post by sue99
Can you please include a picture of Figure 1? as I believe this question is connected with harmonic/fundamental frequencies and I need to see the diagram to be sure


Sorry, my bad
Physics33.png

Here's a link to the actual paper: http://filestore.aqa.org.uk/resources/physics/AQA-74071-SQP.PDF
Its question 3.
The markscheme can be found here: http://filestore.aqa.org.uk/resources/physics/AQA-74071-SMS.PDF
Reply 4
Avatar for veejn
veejn
1
Original post by Someboady
Sorry, my bad
Physics33.png

Here's a link to the actual paper: http://filestore.aqa.org.uk/resources/physics/AQA-74071-SQP.PDF
Its question 3.
The markscheme can be found here: http://filestore.aqa.org.uk/resources/physics/AQA-74071-SMS.PDF


The distance moved by the tube is d2-d1. The path difference is 2 times that because the wave travels that distance moved at the top of the tube and at the bottom of the tube
Reply 5
Avatar for Someboady
Someboady
OP
17
Original post by veejn
The distance moved by the tube is d2-d1. The path difference is 2 times that because the wave travels that distance moved at the top of the tube and at the bottom of the tube


Well you destroyed my confusion in one sentence....my teacher couldn't even tell me that! Bloody hell that was simple. Thanks very much!
Reply 6
Avatar for sue99
sue99
10
Original post by Someboady
Sorry, my bad
Physics33.png

Here's a link to the actual paper: http://filestore.aqa.org.uk/resources/physics/AQA-74071-SQP.PDF
Its question 3.
The markscheme can be found here: http://filestore.aqa.org.uk/resources/physics/AQA-74071-SMS.PDF


Okay, so this is how I understand it:

for sound to be at a minimum at any point, the waves must have interfered destructively, ie. the path difference is a half number of wavelengths - lamda/2

so wavelength = v / f
= ....

then because the path difference is lamda/2 , you just divide the value of the wavelength by 2
Reply 7
Avatar for Someboady
Someboady
OP
17
Original post by sue99
Okay, so this is how I understand it:

for sound to be at a minimum at any point, the waves must have interfered destructively, ie. the path difference is a half number of wavelengths - lamda/2

so wavelength = v / f
= ....

then because the path difference is lamda/2 , you just divide the value of the wavelength by 2


Yep so path difference is 0.2125m. As veejn mentioned above; the path difference is divided by two and this was what I didn't quite understand. It's because there's the top part of the tube and bottom part of the tube as seen in figure 1. That's why we divide by two since both lengths are equal and when we divide by two, we find the length of just one of the top/bottom part of the tube which is the length that the tubes been extended by.
Thanks for your help! =)
Reply 8
Avatar for sue99
sue99
10
Original post by Someboady
Yep so path difference is 0.2125m. As veejn mentioned above; the path difference is divided by two and this was what I didn't quite understand. It's because there's the top part of the tube and bottom part of the tube as seen in figure 1. That's why we divide by two since both lengths are equal and when we divide by two, we find the length of just one of the top/bottom part of the tube which is the length that the tubes been extended by.
Thanks for your help! =)


Haha you're too nice; I didn't really help at all! :tongue: But I'm glad you understand it now!
Reply 9
Avatar for veejn
veejn
1
Original post by Someboady
Well you destroyed my confusion in one sentence....my teacher couldn't even tell me that! Bloody hell that was simple. Thanks very much!


No worries

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